The main London section of the proposed Crossrail Berkshire-to-Essex infrastructure link could be delayed by a year to shave £1bn off the project's price tag.

Management is being forced to cut costs in light of the Government's austerity drive. A source close to Crossrail said that delaying to 2018 the completion of the main section under central London would bring the budget "closer to £15bn" than its current £15.9bn forecast.

Subsequent sections would not be completed until later, though the revised timetable does not appear to have been finalised.

Sources suggested that the initial plans, which include 37 stations along the 72-mile line, meant that more cash would have had to be thrown at the project to get it ready on time. In May, the Rail minister, Theresa Villiers, said she wanted to be sure the long-trumpeted project would provide "value for money".

Crossrail's plans will form part of the comprehensive spending review to be announced in October.